Probiotics are live microorganisms, preferably bacteria, which when administered in adequate amounts to a subject, confer a health benefit to the subject. Some health benefits may be strain specific, i.e., vary by genus and species, but regardless of the type of benefit, to confer the benefit, an effective amount of bacteria must be alive (or viable) at the time of administration. As a result of this overriding concern in the art, considerable research has been done on strategies for dry shelf stability, as well as, enteric coatings to protect the probiotics as they pass through the subject's stomach. Stability is typically measured as a decrease in viable bacteria, for example, a log reduction in colony forming units (cfu) is a ten-fold decrease.
Regarding the concern related to shelf stability, following convention wisdom, those skilled in the art have concentrated their efforts on freeze drying the bacteria and then keeping them dry, usually by using a hydrophobic coating. Nonetheless, activity appears to decrease over time, even in dry environments. In environments where the moisture is about 10% water, activity drops precipitously. For example, US 2005/0266069, para. [0025] alleges a 4 log reduction in 14 days at 37° C. for one variety of encapsulated probiotic in a 10% water environment. Food is typically described as dry (theoretically 0-15% water), semi-moist (15-70% water), or moist (70-90%). Beverages are obviously greater than 90% water. As can be appreciated, if limited to dry environments, a large market segment remains closed to probiotics, or requires dosing with a vast excess of probiotics in the hope that an effective amount will survive.
Accordingly, what is needed are methods for enhancing the shelf stability of probiotics in foods that have greater than 10% water or in beverages.